Luminescent material

ABSTRACT

A luminescent material is disclosed. The luminescent material may include a first compound having a host lattice comprising first ions and oxygen. A first portion of the first ions may be substituted by copper ions. In one embodiment, the host lattice may include silicon, the copper ions may be divalent copper ions and the first compound may have an Olivine crystal structure, β-K 0.2 SO 4  crystal structure, a trigonal Glaserite (K 3 Na(SO 4 ) 2 ) or monoclinic Merwinite crystal structure, a tetragonal Ackermanite crystal structure, a tetragonal crystal structure or an orthorhombic crystal structure. In another embodiment, the copper ions do not act as luminescent ions upon excitation with the ultraviolet or visible light.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent application Ser. No. 11/948,813, filed on Nov. 30, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 11/024,722, filed on Dec. 30, 2004, and claims priority from and the benefit of Korean Patent Application No. 10-2004-0042397, filed on Jun. 10, 2004, which is hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to fluorescent materials containing rare earth elements and, more particularly, to such luminescent materials for exciting ultraviolet as well as visible light containing lead- and/or copper-containing compounds.

2. Description of the Related Art

Lead and copper activated materials are known for short wave excitation, e.g. from a low pressure mercury lamp, such as barium disilicate activated by lead (Keith H. Butler, The Pennsylvania State University Press, 1980, S 175, orthosilicate activated by lead (Keith H. Butler, The Pennsylvania State University Press, 1980, S. 181), akermanites activated by lead, or Ca-metasilicate activated by Pb²⁺.

Generally, the maxima of the emission bands of such lead activated phosphors are located between 290 nm and 370 nm at 254 nm excitation. Bariumdisilicate activated by lead is an U.V. emitting phosphor which currently is used in sun parlor lamps.

Lead has in the ground state ¹S₀ two outer electrons. The electron configuration of the ground state is d¹⁰s², so that the lowest excited state has d¹⁰sp configuration. The excited sp configuration has four levels, ³P₀, ³P₁, ³P₂ and ¹P₁, which can be achieved between 165.57 nm (³P₀) and 104.88 nm (¹P₁) in the free ion. Transitions between ¹S₀ and ¹P₁ excited level are allowed by all selection rules. While transitions between ¹S₀ and ³P₀ are only allowed with the lowest symmetry, transitions between ¹S₀ and ³P₁ as well as ³P₂ are allowed only under certain conditions. However, excitation between 180 and 370 nm has the same emission. Excitation with wavelength longer than 370 nm is not possible.

Otherwise, luminescent materials are known having lead as a host lattice component. Molybdate phosphors containing MoO₄ ²⁻ centers are described in Bernhardt, H. J., Phys. Stat. Sol. (a), 91, 643, 1985. PbMoO₄ shows at room temperature red emission with an emission maximum at 620 nm under photoexcitation at 360 nm.

However, such emission is not caused by lead itself. In molybdates the luminescence properties are not caused by the metal ion M²⁺ (M²⁺MoO₄ where M²⁺=Ca, Sr, Cd, Zn, Ba, Pb etc). Here, defect centers of MoO₄ ²⁻ ions coupled to O²⁻-ion vacancies seem to be the reason. Nevertheless, the Pb²⁺-ion influences the preferred emission properties because it stabilizes the host lattice.

As a familiar example, tungstates (Ca,Pb)WO₄ as mixed crystals have a strong green emission with high quantum output of 75% (Blasse, G, Radiationless processes in luminescent materials, in Radiationless Processes, DiBartolo, B., Ed. Plenum Press, New York, 1980, 287). Under 250 nm excitation PbWO₄ shows blue emission and under 313 nm excitation PbWO₄ has an orange emission band, which can be caused by Schottky defects or by impurity ions (Phosphor Handbook, edited under the Auspice of Phosphor Research Society, CRC Press New York, 1998, S 205).

Copper was used as a monovalent activator in orthophosphates (Wanmaker, W. L. and Bakker, C., J. Electrochem. Soc., 106, 1027, 1959) with an emission maximum at 490 nm. The ground state of monovalent copper is a filled shell 3d¹⁰. That is the level ¹S₀. After exciting the lowest excited configuration is 3d⁹4s. This configuration has two terms, ³D and ¹D. The next higher configuration, 3d⁹4p, gives 6 terms ³P°, ³F°, 3D°, ¹F°, ¹D° and ¹P°. The transitions between the ground state ¹S₀ and the ¹D or ³D are forbidden by parity or spin, respectively. In copper ions, the excitation to the crystal field levels of 4p terms are allowed. Emission will be got either by a direct return from the crystal field odd state to the ground state or by a combination of transitions first from the odd state to a crystal field level and after that a second transition from these ³D or ¹D state of the 3d⁹4s configuration to the ground state.

The ground state of bivalent copper has 3d⁹-configuration. That is the level ²D_(5/2). In the bivalent copper, one of the d-electrons can be excited to the 4s or 4p orbital. The lowest exciting configuration is the 3d⁸4s with two quartet terms ⁴F, ⁴P and four doublet terms, ²F, ²D, ²P and ²G without emission caused by forbidden transitions. The higher exciting configuration is the 3d⁸4p-configuration with four terms ⁴D°, ⁴G°, ⁴F°, and ⁴P°, where emission can occur.

Copper activated or co-activated sulphide-phosphors are well known and they are commercial used for cathode ray tubes. The green-emitting ZnS:Cu, Al (wherein, the copper is used as activator and Al is used as co-activator) is very important in CRT applications.

In zinc-sulphide phosphors, the luminescent materials can be classified into five kinds, depending on the relative ratio of the concentration of activators and co-activators (van Gool, W., Philips Res. Rept. Suppl., 3, 1, 1961). Here, the luminescent centers are formed from deep donors or deep acceptors, or by their association at the nearest-neighbor sites (Phosphor Handbook, edited under the Auspice of Phosphor Research Society, CRC Press New York, 1998, S. 238).

Orthophosphates activated by copper (Wanmaker, W. L., and Spier, H. L., JECS 109 (1962), 109), and pyrophosphates, alumosilicates, silicates, and tripolyphosphates all activated by copper are described in “Keith H. Butler, The Pennsylvania State University Press, 1980, S. 281”. However, such phosphors can only be used for a short wave U.V. excitation. Because of their unstable chemical properties and their temperature behavior, they cannot be used in fluorescent lamps.

It has been observed that conventional luminescent materials are generally unstable in water, air humidity, water steam and polar solvents.

SUMMARY OF THE INVENTION

One embodiment exemplarily described herein can be generally characterized as a luminescent material for a light emitting diode (LED) that includes a first compound including a host lattice and a luminescent ion within the host lattice. The host lattice may include first ions and oxygen. A first portion of the first ions may be substituted by divalent copper ions. The first compound may emit light upon excitation with ultraviolet light or visible light emitted by the LED. The first compound may have an Olivine crystal structure, a β-K_(0.2)SO₄ crystal structure, a trigonal Glaserite (K₃Na(SO₄)₂) or monoclinic Merwinite crystal structure, a tetragonal Ackermanite crystal structure, a tetragonal crystal structure or an orthorhombic crystal structure.

According to another embodiment, the luminescent ion includes at least one of Bi, Sn, Sb, Sc, Y, La, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. According to another embodiment, the first compound includes Ge. According to another embodiment, the luminescent material further includes at least one second compound selected from the group consisting of an aluminate, a silicate, an antimonite, a germinate, a germinate-silicate and a phosphate. According to another embodiment, the luminescent material emits white light upon excitation with ultraviolet light or visible light.

Another embodiment exemplarily described herein can be generally characterized as a luminescent material for a light emitting diode (LED) that includes a first compound including a host lattice and a luminescent ion within the host lattice. The host lattice may include first ions and oxygen. A first portion of the first ions may be substituted by copper ions. The first compound may emit light upon excitation with ultraviolet light or visible light emitted by the LED. However, the copper ions do not act as luminescent ions upon excitation with the ultraviolet light or visible light. An additional object of the present invention is to provide lead and/or copper doped luminescent materials, which give high color temperature range about 2,000K to 8,000K or 10,000K and CRI over 90 in LED.

DETAILED DESCRIPTION

According to embodiments exemplarily described herein, a luminescent material may include one or more lead- and/or copper-containing chemical compounds. The luminescent material may be excited by UV and/or visible (e.g., blue) light. In some embodiments, the lead- and/or copper-containing chemical compounds may be generally characterized as including a host lattice having anions and cations. In some embodiments, at least a portion of the cations are divalent cations. In some embodiments, the divalent cations include alkaline earth ions. In some embodiments, at least a portion of the divalent cations of the host lattice are substituted by divalent lead and/or divalent copper ions.

As mentioned above, conventional luminescent materials are generally unstable in water, air humidity, water steam and polar solvents. However, due to a higher covalency and a lower basicity, the substitutionally-incorporated divalent lead and/or divalent copper ions in the host lattice of the chemical compound yields luminescent materials having improved resistance against water, air humidity and polar solvents.

The divalent lead and/or divalent copper ions within the host lattice do not act as activators (also referred to herein as “luminescent ions”) and, therefore do not luminance. Rather, it has been found that these ions tend to influence the crystal field splitting as well as the covalency of the chemical compound. As a result, the substitutional incorporation of divalent lead and/or copper ions within the host lattice tends to influence luminescent-optical properties of the chemical compounds so as to improve luminescent intensity and desirably shift the emission maxima, color points, and shape of emission spectra.

It has been found that phosphors having chemical compounds that contain substitutionally-incorporated divalent lead and/or divalent copper ions show improved emission intensities as compared with phosphors having chemical compounds that do not contain substitutionally-incorporated divalent lead and/or divalent copper ions.

In addition, it has been found that phosphors having chemical compounds that contain substitutionally-incorporated divalent lead and/or divalent copper ions tend to show improved luminescent properties for excitation wavelength higher than about 360 nm. At excitation wavelengths higher than about 360 nm, the divalent lead and/or divalent copper ions do not exhibit their own radiation transfers due to the energy levels of their electron configuration, so that any kind of exciting radiation cannot be lost. Furthermore, by substitutionally incorporating divalent lead and/or divalent copper ions, the emission wavelength can be shifted to higher or lower energies as desired.

Lead ions having an ionic radius of 119 μm can substitute the alkaline earth ions Ca having an ionic radius of 100 μm and Sr having an ionic radius of 118 μm very easily. The electro negativity of lead with 1.55 is much higher than that of Ca (1.04) and Sr (0.99). The preparation of substances containing lead is complicated due to the possibility of an oxidation of these ions in reducing atmospheres. For the preparation of lead-containing compounds, which need reducing atmosphere, special preparation processes are necessary.

The influence of substitutionally-incorporated divalent lead ions in the crystal field on the shifting of emission characteristics depends upon the substituted ions. When divalent lead ions substitute Sr or Ba in Eu-activated aluminates and/or silicates, the emission maximum tends to be shifted to longer wavelengths due to smaller ionic radii of Pb as compared with the ionic radii of Ba and Sr. That leads to a stronger crystal field surrounding the activator ion.

A similar effect shows the substitution of divalent copper ions for alkaline earth ions. Here, an additional influence is effective. Due to the higher ionic potential of copper as a quotient of ionic charge and ionic radius compared to the bigger alkaline earth ions, the copper ions can attract the neighboring oxygen ions stronger than the alkaline earth ions. So the substitution of the bigger alkaline earth ions Ca, Sr and Ba by copper leads to a stronger crystal field in the surrounding of the activator ions, too. Thus, the shape of emission bands can be influenced, the shifting of the emission peak to longer wavelength is connected in a broadening of the emission curves for band emission. In addition, it should be possible to increase the intensity of emission by substitution of ions copper and lead. Generally, the shifting of emission peaks to longer or shorter wavelengths are desirable in the field of LED lighting. Here, it is necessary to realize a fine tuning to get a special wavelength for desired color points as well as for better brightness of optical devices. By using cations, copper and lead, such a fine tuning should be possible.

As described above, the luminescent material may include one or more chemical compounds such as, for example, aluminates, silicates, antimonates, germinates, germinate-silicates, and/or phosphates. Exemplary embodiments of these luminescent materials are described in greater detail below.

EXAMPLE 1

Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing aluminates exemplarily characterized according to the formula as follows: a(M′O).b(M″₂O).c(M″X).dAl₂O₃ .e(M′″O).f(M″″₂O₃).g(M′″″_(o)O_(p)).h(M″″″_(x)O_(y))  (1)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be one or more monovalent elements, for example, Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be one or more divalent elements, for example, Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be one or more trivalent elements, for example, Sc, B, Ga, In, and/or any combination thereof; M′″″ may be Si, Ge, Ti, Zr, Mn, V, Nb, Ta, W, Mo, and/or any combination thereof; M″″″ may be Bi, Sn, Sb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦2; 0≦c≦2; 0<d≦8; 0<e≦4; 0≦f≦3; 0≦g≦8; 0<h≦2; 1≦o≦2; 1≦p≦5; 1≦x≦2; and 1≦y≦5. a(M′O).b(M″₂O).c(M″X).4−a−b−c(M′″O).7(Al₂O₃).d(B₂O₃).e(Ga₂O₃).f(SiO₂).g(GeO₂).h(M″″_(x)O_(y))  (2)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be one or more monovalent elements, for example, Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be one or more divalent elements, for example, Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Bi, Sn, Sb, Sc, Y, La, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and any combination thereof; X may be F, Cl, Br, I, and any combination thereof; 0<a≦4; 0≦b≦2; 0≦c≦2; 0≦d≦1; 0≦e≦1; 0≦f≦1; 0≦g≦1; 0<h≦2; 1≦x≦2; and 1≦y≦5.

The preparation of copper- as well as lead-containing luminescent materials may be a basic solid state reaction. Pure starting materials without any impurities, e.g. iron, may be used. Any starting material which may transfer into oxides via a heating process may be used to form oxygen dominated phosphors.

Examples of Preparation:

Preparation of the Luminescent Material Having Formula (3) Cu_(0.02)Sr_(3.98)Al₁₄O₂₅:Eu  (3)

Starting materials: CuO, SrCO₃, Al(OH)₃, Eu₂O₃, and/or any combination thereof.

The starting materials in the form of oxides, hydroxides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, e.g., H₃BO₃. The mixture may be fired in an alumina crucible in a first step at about 1,200° C. for about one hour. After milling the pre-fired materials a second firing step at about 1,450° C. in a reduced atmosphere for about 4 hours may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum of about 494 nm.

TABLE 1 copper containing Eu²⁺-activated aluminate compared with Eu²⁺- activated aluminate without copper at about 400 nm excitation wavelength Compound Compound containing copper without copper Cu_(0.02)Sr_(3.98)Al₁₄O₂₅: Eu Sr₄Al₁₄O₂₅: Eu Luminous density (%) 103.1 100 Wavelength (nm) 494 493

Preparation of the Luminescent Material Having Formula (4) Pb_(0.05)Sr_(3.95)Al₁₄O₂₅:Eu  (4)

Starting materials: PbO, SrCO₃, Al₂O₃, Eu₂O₃, and/or any combination thereof.

The starting materials in form of very pure oxides, carbonates, or other components which may decompose thermically into oxides, may be mixed in stoichiometric proportion together with small amounts of flux, for example, H₃BO₃. The mixture may be fired in an alumina crucible at about 1,200° C. for about one hour in the air. After milling the pre-fired materials a second firing step at about 1,450° C. in air for about 2 hours and in a reduced atmosphere for about 2 hours may be followed. Then the material may be milled, washed, dried, and sieved. The resulting luminescent material may have an emission maximum of from about 494.5 nm.

TABLE 2 lead-containing Eu²⁺-activated aluminate compared with Eu²⁺-activated aluminate without lead at about 400 nm excitation wavelength Compound Lead-containing compound without lead Pb_(0.05)Sr_(3.95)Al₁₄O₂₅: Eu Sr₄Al₁₄O₂₅: Eu Luminous density (%) 101.4 100 Wavelength (nm) 494.5 493

TABLE 3 optical properties of some copper-and/or lead-containing aluminates excitable by long wave ultraviolet and/or by visible light and their luminous density in % at 400 nm excitation wavelength Peak wave length of lead- Luminous density at 400 nm and/or copper Possible excitation compared containing Peak wave length of excitation with compounds not materials materials without Composition range(nm) containing copper/lead (%) (nm) lead/copper (nm) Cu_(0.5)Sr_(3.5)Al₁₄O₂₅: Eu 360-430 101.2 495 493 Cu_(0.02)Sr_(3.98)Al₁₄O₂₅: Eu 360-430 103.1 494 493 Pb_(0.05)Sr_(3.95)Al₁₄O₂₅: Eu 360-430 101.4 494.5 493 Cu_(0.01)Sr_(3.99)Al_(13.995)Si_(0.005)O₂₅: 360-430 103 494 492 Eu Cu_(0.01)Sr_(3.395)Ba_(0.595)Al₁₄O₂₅: Eu, 360-430 100.8 494 493 Dy Pb_(0.05)Sr_(3.95)Al_(13.95)Ga_(0.05)O₂₅: Eu 360-430 101.5 494 494

EXAMPLE 2

Luminescent materials for ultraviolet light or visible light excitation comprise lead and/or copper doped aluminates according to the formula as follows: a(M′O).b(M″O).c(Al₂O₃).d(M′″₂O₃).e(M″″O₂).f(M′″″_(x)O_(y))  (5)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M′″ may be B, Ga, In, and/or any combination thereof; M″″ may be Si, Ge, Ti, Zr, Hf, and/or any combination thereof; M′″″ may be Bi, Sn, Sb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or any combination thereof; 0<a≦1; 0≦b≦2; 0<c≦8; 0≦d≦1; 0≦e≦1; 0<f≦2; 1≦x≦2; and 1≦y≦5.

The luminous peak and density of Example 2 are described in Table 7, which will be shown below.

Example of Preparation:

Preparation of the Luminescent Material Having Formula (6) Cu_(0.05)Sr_(0.95)Al_(1.9997)Si_(0.0003)O₄:Eu  (6)

Starting materials: CuO, SrCO₃, Al₂O₃, SiO₂, Eu₂O₃, and/or any combination thereof.

The starting materials in the form of, for example, pure oxides and/or as carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, AlF₃. The mixture may be fired in an alumina crucible at about 1,250° C. in a reduced atmosphere for about 3 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum of about 521.5 nm.

TABLE 4 copper containing Eu²⁺-activated aluminate compared with Eu²⁺- activated aluminate without copper at about 400 nm excitation wavelength Compound Compound containging copper without copper Cu_(0.05)Sr_(0.95)Al_(1.9997)Si_(0.0003)O₄: Eu SrAl₂O₄: Eu Luminous density 106 100 (%) Wavelength (nm) 521.5 519

Preparation of the Luminescent Material Having Formula (7) Cu_(0.12)BaMg_(1.88)Al₁₆O₂₇:Eu  (7)

Starting materials: CuO, MgO, BaCO₃, Al(OH)₃, Eu₂O₃, and/or any combination thereof.

The starting materials in the form of, for example, pure oxides, hydroxides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, AlF₃. The mixture may be fired in an alumina crucible at about 1,420° C. in a reduced atmosphere for about 2 hours. After that the material may be milled, washed, dried, and sieved. The resulting luminescent material may have an emission maximum of about 452 nm.

TABLE 5 copper-containing Eu²⁺-activated aluminate compared with copper not doped Eu²⁺-activated aluminate at 400 nm excitation wavelength Compound Comparison containing copper without copper Cu_(0.12)BaMg_(1.88)Al₁₆O₂₇: Eu BaMg₂Al₁₆O₂₇: Eu Luminous density (%) 101 100 Wavelength (nm) 452 450

Preparation of the Luminescent Material Having Formula (8) Pb_(0.1)Sr_(0.9)Al₂O₄:Eu  (8)

Starting materials: PbO, SrCO₃, Al(OH)₃, Eu₂O₃, and/or any combination thereof.

The starting materials in form of, for example, pure oxides, hydroxides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, H₃BO₃. The mixture may be fired in an alumina crucible at about 1,000° C. for about 2 hours in the air. After milling the pre-fired materials a second firing step at about 1,420° C. in the air for about 1 hour and in a reduced atmosphere for about 2 hours may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum of about 521 nm.

TABLE 6 lead-containing Eu²⁺-activated aluminate compared with Eu²⁺- activated aluminate without lead at about 400 nm excitation wavelength Lead-containing compound Compound without lead Pb_(0.1)Sr_(0.9)Al₂O₄: Eu SrAl₂O₄: Eu Luminous density (%) 102 100 Wavelength (nm) 521 519

Results obtained in regard to copper and/or lead doped aluminates are shown in table 7.

TABLE 7 optical properties of some copper-and/or lead-containing aluminates excitable by long wave ultraviolet and/or by visible light and their luminous density in % at 400 nm excitation wavelength Peak wave Luminous density at length of Possible 400 nm excitation lead/copper excitation compared with doped Peak wave length of range copper/lead not doped materials materials without Composition (nm) compounds (%) (nm) lead/copper (nm) Cu_(0.05)Sr_(0.95)Al_(1.9997)Si_(0.0003)O₄: Eu 360-440 106   521.5 519 Cu_(0.2)Mg_(0.7995)Li_(0.0005)Al_(1.9)Ga_(0.1)O₄: 360-440 101.2 482 480 Eu, Dy Pb_(0.1)Sr_(0.9)Al₂O₄: Eu 360-440 102 521 519 Cu_(0.05)BaMg_(1.95)Al₁₆O₂₇: Eu, Mn 360-400 100.5 451, 515 450, 515 Cu_(0.12)BaMg_(1.88)Al₁₆O₂₇: Eu 360-400 101 452 450 Cu_(0.01)BaMg_(0.99)Al₁₀O₁₇: Eu 360-400 102.5 451 449 Pb_(0.1)BaMg_(0.9)Al_(9.5)Ga_(0.5)O₁₇: Eu, 360-400 100.8 448 450 Dy Pb_(0.08)Sr_(0.902)Al₂O₄: Eu, Dy 360-440 102.4 521 519 Pb_(0.2)Sr_(0.8)Al₂O₄: Mn 360-440 100.8 658 655 Cu_(0.06)Sr_(0.94)Al₂O₄: Eu 360-440 102.3 521 519 Cu_(0.05)Ba_(0.94)Pb_(0.06)Mg_(0.95)Al₁₀O₁₇: 360-440 100.4 451 449 Eu Pb_(0.3)Ba_(0.7)Cu_(0.1)Mg_(1.9)Al₁₆O₂₇: Eu 360-400 100.8 452 450 Pb_(0.3)Ba_(0.7)Cu_(0.1)Mg_(1.9)Al₁₆O₂₇: Eu, 360-400 100.4 452, 515 450, 515 Mn

EXAMPLE 3

Luminescent materials for ultraviolet light or visible light excitation comprise lead and/or copper doped silicates according to the formula as follows: a(M′O).b(M″O).c(M′″X).d(M′″₂O).e(M″″₂O₃).f(M′″″_(o)O_(p)).g(SiO₂).h(M″″″_(x)O_(y))  (9)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M′″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M″″ may be Al, Ga, In, and/or any combination thereof; M′″″ may be Ge, V, Nb, Ta, W, Mo, Ti, Zr, Hf, and/or any combination thereof; M″″″ may be Bi, Sn, Sb, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or any combination thereof; X may be F, Cl, Br, I, and any combination thereof; 0<a≦2; 0<b≦8; 0≦c≦4; 0≦d≦2; 0≦e≦2; 0≦f≦2; 0<g≦10; 0<h≦5; 1≦o≦2; 1≦p≦5; 1≦x≦2; and 1≦y≦5.

The copper-containing silicates exemplarily described herein may, in some embodiments, contain SiO₄ and be characterized as having an Olivine structure (orthorhombic) or β-K_(0.2)SO₄ structure (orthorhombic); contain Si₂O₈ and be characterized as having a trigonal Glaserite (K₃Na(SO₄)₂) or monoclinic Merwinite structure; contain Si₂O₇ and be characterized as having a tetragonal Ackermanite structure; contain SiO₅ and be characterized as having a tetragonal structure; and/or contain Si₂O₅ and be characterized as having an orthorhombic structure.

The superior luminous density of Example 3 can be seen below.

Example of Preparation:

Preparation of the Luminescent Material Having Formula (10) Cu_(0.05)Sr_(1.7)Ca_(0.25)SiO₄: Eu  (10)

Starting materials: CuO, SrCO₃, CaCO₃, SiO₂, Eu₂O₃, and/or any combination thereof.

The starting materials in the form of pure oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH₄Cl. The mixture may be fired in an alumina crucible at about 1,200° C. in an inert gas atmosphere (e.g., N₂ or noble gas) for about 2 hours. Then the material may be milled. After that, the material may be fired in an alumina crucible at about 1,200° C. in a slightly reduced atmosphere for about 2 hours. Then, the material may be milled, washed, dried, and sieved. The resulting luminescent material may have an emission maximum at about 592 nm.

TABLE 8 copper-containing Eu²⁺-activated silicate compared with Eu²⁺- activated silicate without copper at about 400 nm excitation wavelength Copper-containing Compound without compound copper Cu_(0.05)Sr_(1.7)Ca_(0.25)SiO₄: Eu Sr_(1.7)Ca_(0.3)SiO₄: Eu Luminous density (%) 104 100 Wavelength (nm) 592 588

Preparation of the Luminescent Material Having Formula (11): Cu_(0.2)Ba₂Zn_(0.2)Mg_(0.6)Si₂O₇:Eu  (11)

Starting materials: CuO, BaCO₃, ZnO, MgO, SiO₂, Eu₂O₃, and/or any combination thereof.

The starting materials in the form of very pure oxides and carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH₄Cl. In a first step the mixture may be fired in an alumina crucible at about 1,100° C. in a reduced atmosphere for about 2 hours. Then the material may be milled. After that the material may be fired in an alumina crucible at about 1,235° C. in a reduced atmosphere for about 2 hours. Then that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 467 nm.

TABLE 9 copper-containing Eu²⁺-activated silicate compared with Eu²⁺-activated silicate without copper at 400 nm excitation wavelength Copper-containing compound Compound without copper Cu_(0.2)Sr₂Zn_(0.2)Mg_(0.6)Si₂O₇: Eu Sr₂Zn₂Mg_(0.6)Si₂O₇: Eu Luminous 101.5 100 density (%) Wavelength 467 465 (nm)

Preparation of the Luminescent Material Having Formula (12) Pb_(0.1)BaO_(0.95)Sr_(0.95)Si_(0.998)Ge_(0.002)O₄:Eu  (12)

Starting materials: PbO, SrCO₃, BaCO₃, SiO₂, GeO₂, Eu₂O₃, and/or any combination thereof.

The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH₄Cl. The mixture may be fired in an alumina crucible at about 1,000° C. for about 2 hours in the air. After milling the pre-fired materials a second firing step at 1,220° C. in air for 4 hours and in reducing atmosphere for 2 hours may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 527 nm.

TABLE 10 lead-containing Eu²⁺-activated silicate compared with Eu²⁺-activated silicate without lead at about 400 nm excitation wavelength Compound Lead-containing compound without lead Pb_(0.1)Ba_(0.95)Sr_(0.95)Si_(0.998)Ge_(0.002)O₄: Eu BaSrSiO₄: Eu Luminous 101.3 100 density (%) Wavelength (nm) 527 525

Preparation of the Luminescent Material Having Formula (13) Pb_(0.25)Sr_(3.75)Si₃O₈Cl₄:Eu  (13)

Starting materials: PbO, SrCO₃, SrCl₂, SiO₂, Eu₂O₃, and any combination thereof.

The starting materials in the form of oxides, chlorides, and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH₄Cl. The mixture may be fired in an alumina crucible in a first step at about 1,100° C. for about 2 hours in the air. After milling the pre-fired materials a second firing step at about 1,220° C. in the air for about 4 hours and in a reduced atmosphere for about 1 hour may be followed. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 492 nm.

TABLE 11 lead-containing Eu²⁺-activated chlorosilicate compared with Eu²⁺- activated chlorosilicate without lead at 400 nm excitation wavelength Lead-containing compound Compound without lead Pb_(0.25)Sr_(3.75)Si₃O₈Cl₄: Eu Sr₄Si₃O₈Cl₄: Eu Luminous 100.6 100 density (%) Wavelength (nm) 492 490

Results obtained with respect to copper- and/or lead-containing silicates are shown in table 12.

TABLE 12 optical properties of some copper- and/or lead-containing rare earth activated silicates excitable by long wave ultraviolet and/or by visible light and their luminous density in % at about 400 nm excitation wavelength Peak wave Luminous density at length Possible 400 nm excitation of lead-and/or Peak wave length excitation compared with copper- of materials range copper/lead not doped containing without Composition (nm) compounds (%) materials (nm) lead/copper (nm) Pb_(0.1)Ba_(0.95)Sr_(0.95)Si_(0.998)Ge_(0.002)O₄: 360-470 101.3 527 525 Eu Cu_(0.02)(Ba,Sr,Ca,Zn)_(1.98)SiO₄: 360-500 108.2 565 560 Eu Cu_(0.05)Sr_(1.7)Ca_(0.25)SiO₄: Eu 360-470 104 592 588 Cu_(0.05)Li_(0.002)Sr_(1.5)Ba_(0.448)SiO₄: 360-470 102.5 557 555 Gd, Eu Cu_(0.2)Sr₂Zn_(0.2)Mg_(0.6)Si₂O₇: Eu 360-450 101.5 467 465 Cu_(0.02)Ba_(2.8)Sr_(0.2)Mg_(0.98)Si₂O₈: 360-420 100.8 440, 660 438, 660 Eu, Mn Pb_(0.25)Sr_(3.75)Si₃O₈Cl₄: Eu 360-470 100.6 492 490 Cu_(0.2)Ba_(2.2)Sr_(0.75)Pb_(0.05)Zn_(0.8)Si₂O₈: 360-430 100.8 448 445 Eu Cu_(0.2)Ba₃Mg_(0.8)Si_(1.99)Ge_(0.01)O₈: 360-430 101 444 440 Eu Cu_(0.5)Zn_(0.5)Ba₂Ge_(0.2)Si_(1.8)O₇: Eu 360-420 102.5 435 433 Cu_(0.8)Mg_(0.2)Ba₃Si₂O₈: Eu, Mn 360-430 103 438, 670 435, 670 Pb_(0.15)Ba_(1.84)Zn_(0.01)Si_(0.99)Zr_(0.01)O₄: 360-500 101 512 510 Eu Cu_(0.2)Ba₅Ca_(2.8)Si₄O₁₆: Eu 360-470 101.8 495 491

EXAMPLE 4

Luminescent materials for ultraviolet light or visible light excitation comprise lead and/or copper-containing antimonates according to the formula as follows: a(M′O).b(M″₂O).c(M′X).d(Sb₂O₅).e(M′″O).f(M″″_(x)O_(y))  (14)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Bi, Sn, Sc, Y, La, Pr, Sm, Eu, Tb, Dy, Gd, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦2; 0≦c≦4; 0≧d≦8; 0≦e≦8; 0<f≦2; 1≦x≦2; and 1≦y≦5.

Examples of Preparation:

Preparation of the Luminescent Material Having Formula (15) Cu_(0.2)Mg_(0.7)Li_(0.2)Sb₂O₇:Mn  (15)

Starting materials: CuO, MgO, Li₂O, Sb₂O₅, MnCO₃, and/or any combination thereof.

The starting materials in the form of oxides may be mixed in stoichiometric proportion together with small amounts of flux. In a first step the mixture may be fired in an alumina crucible at about 985° C. in the air for about 2 hours. After pre-firing the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,200° C. in an atmosphere containing oxygen for about 8 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 626 nm.

TABLE 13 copper-containing antimonate compared with antimonate without copper at about 400 nm excitation wavelength Copper-containing compound Comparison without copper Cu_(0.2)Mg_(1.7)Li_(0.2)Sb₂O₇: Mn Mg₂Li_(0.2)Sb₂O₇: Mn Luminous 101.8 100 density (%) Wavelength 652 650 (nm)

Preparation of the Luminescent Material Having Formula (16) Pb_(0.006)Ca_(0.6)Sr_(0.394)Sb₂O₆  (16)

Starting materials: PbO, CaCO₃, SrCO₃, Sb₂O₅, and/or any combination thereof.

The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux. In a first step the mixture may be fired in an alumina crucible at about 975° C. in the air for about 2 hours. After pre-firing the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,175° C. in the air for about 4 hours and then in an oxygen-containing atmosphere for about 4 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 637 nm.

TABLE 14 lead-containing antimonate compared with antimonate without lead at 400 nm excitation wavelength Lead-containing compound Compound without lead Pb_(0.006)Ca_(0.6)Sr_(0.394)Sb₂O₆ Ca_(0.6)Sr_(0.4)Sb₂O₆ Luminous 102 100 density (%) Wavelength (nm) 637 638

Results obtained in respect to copper- and/or lead-containing antimonates are shown in table 15.

TABLE 15 optical properties of some copper and/or lead-containing antimonates excitable by long wave ultraviolet and/or by visible light and their luminous density in % at about 400 nm excitation wavelength Luminous density at 400 nm Peak wave excitation length of compared with Peak wave length materials Possible copper/lead not of lead-and/or without excitation doped compounds copper-containing lead/copper Composition range (nm) (%) materials (nm) (nm) Pb_(0.2)Mg_(0.002)Ca_(1.798)Sb₂O₆F₂: Mn 360-400 102 645 649 Cu_(0.15)Ca_(1.845)Sr_(0.005)Sb_(1.998)Si_(0.002)O₇: 360-400 101.5 660 658 Mn Cu_(0.2)Mg_(1.7)Li_(0.2)Sb₂O₇: Mn 360-400 101.8 652 650 Cu_(0.2)Pb_(0.01)Ca_(0.79)Sb_(1.98)Nb_(0.02)O₆: Mn 360-400 98.5 658 658 Cu_(0.01)Ca_(1.99)Sb_(1.9995)V_(0.0005)O₇: Mn 360-400 100.5 660 657 Pb_(0.006)Ca_(0.6)Sr_(0.394)Sb₂O₆ 360-400 102 637 638 Cu_(0.02)Ca_(0.9)Sr_(0.5)Ba_(0.4)Mg_(0.18)Sb₂O₇ 360-400 102.5 649 645 Pb_(0.198)Mg_(0.004)Ca_(1.798)Sb₂O₆F₂ 360-400 101.8 628 630

EXAMPLE 5

Luminescent materials for ultraviolet light or visible light excitation comprise lead- and/or copper-containing germanates and/or a germanate-silicates exemplarily characterized according to the formula as follows: a(M′O)b(M″₂O)c(M″X)dGeO₂ e(M′″O)f(M″″₂O₃)g(M′″″_(o)O_(p))h(M″″″_(x)O_(y))  (17)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, and/or any combination thereof; M″″ may be Sc, Y, B, Al, La, Ga, In, and/or any combination thereof; Mm′″″ may be Si, Ti, Zr, Mn, V, Nb, Ta, W, Mo, and/or any combination thereof; M″″″ may be Bi, Sn, Pr, Sm, Eu, Gd, Dy, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦2; 0≦c≦10; 0≦d≦10; 0≦e≦14; 0≦f≦14; 0≦g≦10; 0≦h≦2; 1≦o≦2; 1≦p≦5; 1≦x≦2; and 1≦y≦5.

Example of Preparation:

Preparation of the Luminescent Material Having Formula (18) Pb_(0.004)Ca_(1.99)Zn_(0.006)Ge_(0.8)Si_(0.2)O₄:Mn  (18)

Starting materials: PbO, CaCO₃, ZnO, GeO₂, SiO₂, MnCO₃, and/or any combination thereof,

The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH₄Cl. In a first step the mixture may be fired in an alumina crucible at about 1,200° C. in an oxygen-containing atmosphere for about 2 hours. Then, the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,200° C. in oxygen containing atmosphere for about 2 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 655 nm.

TABLE 16 lead-containing Mn-activated germanate compared with Mn-activated germinate without lead at about 400 nm excitation wavelength Comparison without Copper-containing compound copper Pb_(0.004)Ca_(1.99)Zn_(0.006)Ge_(0.8)Si_(0.2)O₄: Ca_(1.99)Zn_(0.01)Ge_(0.8)Si_(0.2)O₄: Mn Mn Luminous 101.5 100 density (%) Wavelength 655 657 (nm)

Preparation of the Luminescent Material Having Formula (19) Cu_(0.46)Sr_(0.54)Ge_(0.6)Si_(0.4)O₃:Mn  (19)

Starting materials: CuO, SrCO₃, GeO₂, SiO₂, MnCO₃, and/or any combination thereof.

The starting materials in the form of oxides and/or carbonates may be mixed in stoichiometric proportions together with small amounts of flux, for example, NH₄Cl. In a first step the mixture may be fired in an alumina crucible at about 1,100° C. in an oxygen-containing atmosphere for about 2 hours. Then, the material may be milled again. In a second step the mixture may be fired in an alumina crucible at about 1,180° C. in an oxygen-containing atmosphere for about 4 hours. After that the material may be milled, washed, dried and sieved. The resulting luminescent material may have an emission maximum at about 658 nm.

TABLE 17 copper-containing Mn-activated germanate-silicate compared with Mn- activated germanate-silicate without copper at 400 nm excitation wavelength Compound copper-containing compound without copper Cu_(0.46)Sr_(0.54)Ge_(0.6)Si_(0.4)O₃: Mn SrGe_(0.6)Si_(0.4)O₃: Mn Luminous density 103 100 (%) Wavelength (nm) 658 655

TABLE 18 optical properties of some copper and/or lead-containing germanate- silicates excitable by long wave ultraviolet and/or by visible light and their luminous density in % at about 400 nm excitation wavelength Luminous density at 400 nm excitation Peak wave Peak wave Possible compared with length of lead- length of materials excitation copper/lead not and/or copper- without range containing containing lead/copper Composition (nm) compounds (%) materials (nm) (nm) Pb_(0.004)Ca_(1.99)Zn_(0.006)Ge_(0.8)Si_(0.2)O₄: Mn 360-400 101.5 655 657 Pb_(0.002)Sr_(0.954)Ca_(1.044)Ge_(0.93)Si_(0.07)O₄: 360-400 101.5 660 661 Mn Cu_(0.46)Sr_(0.54)Ge_(0.6)Si_(0.4)O₃: Mn 360-400 103 658 655 Cu_(0.002)Sr_(0.998)Ba_(0.99)Ca_(0.01)Si_(0.98)Ge_(0.02)O₄: 360-470 102 538 533 Eu Cu_(1.45)Mg_(26.55)Ge_(9.4)Si_(0.6)O₄₈: Mn 360-400 102 660 657 Cu_(1.2)Mg_(26.8)Ge_(8.9)Si_(1.1)O₄₈: Mn 360-400 103.8 670 656 Cu₄Mg₂₀Zn₄Ge₅Si_(2.5)O₃₈F₁₀: Mn 360-400 101.5 658 655 Pb_(0.001)Ba_(0.849)Zn_(0.05)Sr_(1.1)Ge_(0.04)Si_(0.96)O₄: 360-470 101.8 550 545 Eu Cu_(0.05)Mg_(4.95)GeO₆F₂: Mn 360-400 100.5 655 653 Cu_(0.05)Mg_(3.95)GeO_(5.5)F: Mn 360-400 100.8 657 653

EXAMPLE 6

Luminescent materials for ultraviolet light or visible light excitation comprise lead and/or copper-containing phosphates exemplarily characterized according to the formula as follows: a(M′O)b(M″₂O)c(M″X)dP₂O₅ e(M′″O)f(M″″₂O₃)g(M′″″O₂)h(M″″″_(x)O_(y))  (20)

wherein M′ may be Pb, Cu, and/or any combination thereof; M″ may be Li, Na, K, Rb, Cs, Au, Ag, and/or any combination thereof; M′″ may be Be, Mg, Ca, Sr, Ba, Zn, Cd, Mn, and/or any combination thereof; M″″ may be Sc, Y, B, Al, La, Ga, In, and/or any combination thereof, Mm′″″ may be Si, Ge, Ti, Zr, Hf; V, Nb, Ta, W, Mo, and/or any combination thereof; M″″″ may be Bi, Sn, Pr, Sm, Eu, Gd, Dy, Ce, Tb, and/or any combination thereof; X may be F, Cl, Br, I, and/or any combination thereof; 0<a≦2; 0≦b≦12; 0≦c≦16; 0<d≦3; 0≦e≦5; 0≦f≦3; 0≦g≦2; 0<h≦2; 1≦x≦2; and 1≦y≦5.

The luminescent materials comprising the lead and/or copper-containing phosphates may be used as compounds for ultraviolet light in a light emitting device.

Examples of Preparation:

Preparation of the Luminescent Material Having Formula (21) Cu_(0.02)Ca_(4.98)(PO₄)₃Cl:Eu  (21)

Starting materials: CuO, CaCO₃, Ca₃(PO₄)₂, CaCl₂, Eu₂O₃, and/or any combination thereof,

The starting materials in the form of oxides, phosphates, and/or carbonates and chlorides may be mixed in stoichiometric proportions together with small amounts of flux. The mixture may be fired in an alumina crucible at about 1,240° C. in reducing atmosphere for about 2 hours. After that the material may be milled, washed, dried and sieved. The luminescent material may have an emission maximum at about 450 nm.

TABLE 19 copper-containing Eu²⁺-activated chlorophosphate compared with Eu²⁺-activated chlorophosphate without copper at about 400 nm excitation wavelength Copper-containing Compound compound without copper Cu_(0.02)Ca_(4.98)(PO₄)₃Cl: Eu Ca₅(PO₄)₃Cl: Eu Luminous density (%) 101.5 100 Wavelength (nm) 450 447

TABLE 20 copper- and/or lead-containing phosphates excitable by long wave ultraviolet and/or by visible light and their luminous density in % at about 400 nm excitation wavelength Luminous density at 400 nm Peak wave length excitation compared of lead/copper- Peak wave length Possible with copper/lead not containing of materials excitation doped compounds materials without Composition range (nm) (%) (nm) lead/copper (nm) Cu_(0.02)Sr_(4.98)(PO₄)₃Cl: Eu 360-410 101.5 450 447 Cu_(0.2)Mg_(0.8)BaP₂O₇: Eu, Mn 360-400 102 638 635 Pb_(0.5)Sr_(1.5)P_(1.84)B_(0.16)O_(6.84): Eu 360-400 102 425 420 Cu_(0.5)Mg_(0.5)Ba₂(P,Si)₂O₈: Eu 360-400 101 573 570 Cu_(0.5)Sr_(9.5)(P,B)₆O₂₄Cl₂: Eu 360-410 102 460 456 Cu_(0.5)Ba₃Sr_(6.5)P₆O₂₄(F,Cl)₂: 360-410 102 443 442 Eu Cu_(0.05)(Ca,Sr,Ba)_(4.95)P₃O₁₂Cl: 360-410 101.5 438, 641 435, 640 Eu, Mn Pb_(0.1)Ba_(2.9)P₂O₈: Eu 360-400 103 421 419

Lead- and/or copper-containing luminescent materials exemplarily described above can be act as converter for light emitting devices, such as ultraviolet as well as blue emitting LEDs, back lights and painting pigments. They can convert the excitation wavelength from the ultraviolet and blue light to longer visible wavelength. According to some embodiments, one or more of the lead- and/or copper-containing luminescent materials exemplarily described above may be used or mixed to produce a luminescent material with a color temperature ranging from about 2,000K to about 8,0000K or about 10,000K and superior color rendering index of greater than about 60 (e.g. between about 60 and about 90, or greater than about 90, or between about 90 and about 95). Thus, for all color temperatures as well as for all color coordinates inside of the white light coordinates, an appropriate luminescent material or mixture thereof can be found. 

1. A luminescent material for a light emitting diode (LED), comprising: a first compound including a host lattice and a luminescent ion within the host lattice, wherein the host lattice comprises first ions and oxygen, wherein a first portion of the first ions is substituted by divalent copper ions, wherein the first compound emits light upon excitation with ultraviolet light or visible light emitted by the LED, wherein the first compound has a trigonal Glaserite (K₃Na(SO₄)₂) crystal structure, a monoclinic Merwinite crystal structure, a tetragonal crystal structure, or an orthorhombic crystal structure, and wherein the first ions comprise at least one of Be, Mg, Ca, Sr, Ba, Zn, Cd and Mn.
 2. The luminescent material of claim 1, wherein the luminescent material has a color temperature ranging from about 2,000K to about 8,000K.
 3. The luminescent material of claim 1, wherein the luminescent material has a color temperature of about 10,000K.
 4. The luminescent material of claim 1, wherein the luminescent material has a color rendering index greater than about
 60. 5. The luminescent material of claim 4, wherein the luminescent material has a color rendering index between about 60 and about
 90. 6. The luminescent material of claim 4, wherein the luminescent material has a color rendering index greater than about
 90. 7. The luminescent material of claim 1, wherein the luminescent ion comprises at least one of Bi, Sn, Sb, Sc, Y, La, In, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
 8. The luminescent material of claim 1, wherein the first compound comprises a silicate.
 9. The luminescent material of claim 8, wherein the first compound comprises Ge. 